8151614: Improve logging in concurrent mark code Summary: Move detailed concurrent mark phase logging to "gc, marking" tags and add a summary "Concurrent Cycle" log message when only using "gc" logging. Reviewed-by: sangheki, brutisso

8151126: Clean up duplicate code for clearing the mark bitmaps Summary: Merge the code to clear the mark bitmap concurrently and in the STW pause. Reviewed-by: jmasa, tbenson

Merge

8151336: Root region scanning should be cancelled and disabled when the ConcurrentMarkThread::run_service() exits Reviewed-by: pliden, tschatzl